1. Field of the Invention
The present invention generally relates to medical monitoring devices, and more particularly, relates to medical devices used to detect artifacts produced by artificial cardiac pacing.
2. Description of the Prior Art
It is known in the art to monitor electrical activity of the human heart for diagnostic and related medical purposes. Such monitoring is also important for determining proper operation of and for permitting programming of implanted cardiac pacers. Medtronic.RTM. Model 5311 pacing system programmer is a state of the art device used for such an application. At times, however, the signal-to-noise ratio of such systems becomes too low to adequately identify the relatively high frequency pacing artifact.
U.S. Pat. No. 4,023,565 issued to Ohlsson describes circuitry for recording EKG signals from multiple lead inputs. Similarly, U.S. Pat. No. 4,263,919 issued to Levin; U.S. Pat. No. 4,170,227 issued to Feldman et al.; and U.S. Pat. No. 4,593,702 issued to Kepski et al., describe multiple electrode systems which combine signals for artifact rejection.
The primary use for multiple electrode systems in the prior art appears to be vectorcardiography. This is a technique whereby the direction of depolarization of the heart is monitored, as well as the amplitude. U.S. Pat. No. 4,121,576 issued to Greensite discusses such a system.
U.S. Pat. No. 4,136,690 issued to Anderson et al., shows a vectorcardiographic system used for arrhythmia analysis. Similar techniques are described in "Rhythm Analysis Using Vectorcardiograms", Transactions on Biomedical Engineering, Volume BME-32 No. 2, February 1985, by Reddy, Murthy and Chatterjee. European Patent 0 086 429 issued to Sanz and U.S. Pat. No. 4,216,780 issued to Rubel et al., also discuss vectorcardiography and related systems.